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Post by billbedford on Dec 28, 2019 10:54:33 GMT
So, back to the earlier point; the compressors don't work off the traction bus cables, because there ARE no traction bus cables. It might be an idea, on new builds at least, to provide a 400v supply from an intermediate car also. The chances of three cars being gapped is fairly unlikely. The problem with traction bus cables is the interconnections between cars. It is all very well for us to sit at computers thinking they are a good idea, but It works on Eurostars, and Pendelios... |
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Post by tjw on Dec 28, 2019 11:50:26 GMT
The problem with traction bus cables is the interconnections between cars. It is all very well for us to sit at computers thinking they are a good idea, but It works on Eurostars, and Pendelios... It also worked on London & South Western (c.100 years ago!) and later Southern Railway EMU stock... They even had the lamps in the compartments wired in series across the line Voltage (like old Christmas tree lights). At least with the earlier stock the cables were fixed to the roof in a box section. I think the 4-COR mainline stock had line Voltage jumpers between units, really handy, the first unit can smash the ice of the conductor rail while the second and third unit can pick up the juice, providing it to all the Motor cars. Of course things did get hot and the arcing lit up the countryside. I suspect that running the line voltage between units is banned / frowned upon, but between cars via jumper cables it is allowed. |
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Post by t697 on Dec 29, 2019 8:45:53 GMT
I suspect that rather than any of these potential train modifications and reconfigurations it will be easier to adjust current rail gaps in the very few locations it's possible to come to a stand with all cars that feed air compressors gapped.
As I pointed out earlier, S stock is not special in this respect.
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Post by bomo on Dec 29, 2019 17:37:20 GMT
All of those can be dealt-with readily, however isn't passing traction current car-to-car they still generally prohibited? (Connor mentions this.)
Not sure about LU, but certainly the National Network seems to gain approval for this on the latest generations of multiple units. AIUI the high tension line runs along the roof. All DC emus built for the former Southern Region network from BR days onwards had/have all of the shoe gear within the unit interconnected. The only slight exception being the 4REP units which had 8 shoes on each of their two motor coaches making 16 in total and these were divided into two groups of 8 with each group having 4 shoes on each motor coach. All the shoes in a group were interconnected but the two groups were not. In all cases the interconnection between vehicles is by low level jumper cables.
As correctly stated some more recent AC units with two pans have a high tension feed along the roof with pigtails between vehicles.
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Post by norbitonflyer on Dec 29, 2019 18:43:27 GMT
All DC emus built for the former Southern Region network from BR days onwards had/have all of the shoe gear within the unit interconnected. I recall reading of one incident where a section had been isolated to allow a train to be evacuated, but another train was mistakenly allowed to move forward to a point where it formed a bridge between the section it was taking power from and the isolated section. Fortunately a quick-thinking staff member supervising the evacuation recognised the significance of the sound of the stalled train's compressors starting up. |
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Post by piccboy on Dec 30, 2019 1:00:11 GMT
I suspect that rather than any of these potential train modifications and reconfigurations it will be easier to adjust current rail gaps in the very few locations it's possible to come to a stand with all cars that feed air compressors gapped. As I pointed out earlier, S stock is not special in this respect. Yes, I do agree adjusting rails gaps to minimise DM cars (Driving Motor) both being gapped would be a sensible precaution. However, with increasing customers being carried and the need for new ATO signalling systems to run more trains per hour, then anything that could adversely effect the running of the service should be looked into. You are correct that S stock is not special in respect of gapping at both DM, but as the newest train on the network, it does have a number of features which improve on previous stocks e.g. being able to reset the tripcock BOTH ends from the cab the driver is currently in. In the event of a rear trip, no more shutting down, going back to the other cab, resetting the tripcock, returning to the driving end, and reopening up. It therefore leads me in my belief that making the S Stock and/or future stock gap proof would be a very desirable thing to do to minimise delays. |
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Post by zbang on Dec 30, 2019 3:41:49 GMT
I recall reading of one incident where a section had been isolated to allow a train to be evacuated, but another train was mistakenly allowed to move forward to a point where it formed a bridge between the section it was taking power from and the isolated section. Fortunately a quick-thinking staff member supervising the evacuation recognised the significance of the sound of the stalled train's compressors starting up.
At least with overhead pickup, with multiple interconnected pan's I'd expect the procedure would be to open the line breaker from the leading shoe/pan' so as to prevent as much arcing and the possibility of bridging a section gap. This ought to be standard procedure, but..... Not sure how well that would work for 3rd/4th rail pickups.
And I'd kind of expect that even when the traction current was discharged, the line breakers would be opened to prevent unintended restarts.
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Post by Dstock7080 on Dec 30, 2019 4:01:14 GMT
You are correct that S stock is not special in respect of gapping at both DM, but as the newest train on the network, it does have a number of features which improve on previous stocks e.g. being able to reset the tripcock BOTH ends from the cab the driver is currently in. In the event of a rear trip, no more shutting down, going back to the other cab, resetting the tripcock, returning to the driving end, and reopening up. It therefore leads me in my belief that making the S Stock and/or future stock gap proof would be a very desirable thing to do to minimise delays. Unfortunately in that respect they are a retrograde step from the previous D Stock, in that NO action was required if the rear trip was operated and no slow-speed operation was necessary. Progress ? |
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Post by jimbo on Dec 30, 2019 8:46:07 GMT
You are correct that S stock is not special in respect of gapping at both DM, but as the newest train on the network, it does have a number of features which improve on previous stocks e.g. being able to reset the tripcock BOTH ends from the cab the driver is currently in. In the event of a rear trip, no more shutting down, going back to the other cab, resetting the tripcock, returning to the driving end, and reopening up. It therefore leads me in my belief that making the S Stock and/or future stock gap proof would be a very desirable thing to do to minimise delays. Unfortunately in that respect they are a retrograde step from the previous D Stock, in that NO action was required if the rear trip was operated and no slow-speed operation was necessary. Progress ? I have a feeling it was 1972TS when someone decided there was no point in stopping a rear-tripped train, so a trip was only effective at the front of the train. It was only when rules for working defective trains were being written that it was realised that if the front cab controller jammed, the driver had to work from the rear cab with the guard riding up front without a tripcock for protection! A second person had to be obtained for extra protection. Rear trips again had to become effective on subsequent trains! |
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Post by countryman on Dec 30, 2019 9:14:00 GMT
Unfortunately in that respect they are a retrograde step from the previous D Stock, in that NO action was required if the rear trip was operated and no slow-speed operation was necessary. Progress ? I have a feeling it was 1972TS when someone decided there was no point in stopping a rear-tripped train, so a trip was only effective at the front of the train. It was only when rules for working defective trains were being written that it was realised that if the front cab controller jammed, the driver had to work from the rear cab with the guard riding up front without a tripcock for protection! A second person had to be obtained for extra protection. Rear trips again had to become effective on subsequent trains! A though has just crossed my mind. I seem to recall that the tripcocks are all on one side of the track. If this is so, then I understand how a front tripcock is tripped, but the tripcock at the rear would be on the wrong side. How would the rear be tripped? I can only think of some kind of lineside obstruction. |
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Post by Dstock7080 on Dec 30, 2019 10:03:37 GMT
A though has just crossed my mind. I seem to recall that the tripcocks are all on one side of the track. If this is so, then I understand how a front tripcock is tripped, but the tripcock at the rear would be on the wrong side. How would the rear be tripped? I can only think of some kind of lineside obstruction. i was trying to find the previous discussion we had on here about 'wrong-road-trainstops' and rear tripping: tripcocks on Chliterns 16x dmui posted a pic at the time which might explain?:  |
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Deleted
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Post by Deleted on Dec 30, 2019 10:06:48 GMT
Looks like Parsons Green
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Post by norbitonflyer on Dec 30, 2019 10:30:26 GMT
train was mistakenly allowed to move forward to a point where it formed a bridge between the section it was taking power from and the isolated section. At least with overhead pickup, with multiple interconnected pan's I'd expect the procedure would be to open the line breaker from the leading shoe/pan' so as to prevent as much arcing and the possibility of bridging a section gap. Not sure how well that would work for 3rd/4th rail pickups.
This was in 3rd rail territory, and the "bridge" was between the collector shoes at opposite ends end of one unit. In OHLE I don't think pantographs are electrically linked. Something like a Pendolino or IEP will only have one pantograph raised (usually the rear one, so that in the event of damage to the OHLE caused by problems with the raised pantograph the other one is already clear of the damaged area). In trains formed of several units (e.g. the 8-car formations of class 315s on TfL Rail), each unit has its own ac feed but there is only a low voltage control connection between them. But I'm now getting confused with how an S stock's electrical connections work. If I've understood correctly, all cars are motored, but only four cars in a train have shoegear, the others taking power from the adjacent car. (So electrically the train is made up of four units). Only two cars have compressors, and if they (or, more correctly, the adjacent DMs they take power from) are both gapped there is no way of powering them from the other shoe-fitted cars. Is that right? |
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Post by t697 on Dec 30, 2019 10:42:57 GMT
You are correct that S stock is not special in respect of gapping at both DM, but as the newest train on the network, it does have a number of features which improve on previous stocks e.g. being able to reset the tripcock BOTH ends from the cab the driver is currently in. In the event of a rear trip, no more shutting down, going back to the other cab, resetting the tripcock, returning to the driving end, and reopening up. It therefore leads me in my belief that making the S Stock and/or future stock gap proof would be a very desirable thing to do to minimise delays. Unfortunately in that respect they are a retrograde step from the previous D Stock, in that NO action was required if the rear trip was operated and no slow-speed operation was necessary. Progress ? Yes, but that mod to D78 stock wasn't standards compliant. I know why it was done and the S stock scheme is a standards compliant solution to the same specific issue, which need not be discussed in detail here. |
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Post by t697 on Dec 30, 2019 10:47:30 GMT
At least with overhead pickup, with multiple interconnected pan's I'd expect the procedure would be to open the line breaker from the leading shoe/pan' so as to prevent as much arcing and the possibility of bridging a section gap. Not sure how well that would work for 3rd/4th rail pickups.
This was in 3rd rail territory, and the "bridge" was between the collector shoes at opposite ends end of one unit. In OHLE I don't think pantographs are electrically linked. Something like a Pendolino or IEP will only have one pantograph raised (usually the rear one, so that in the event of damage to the OHLE caused by problems with the raised pantograph the other one is already clear of the damaged area). In trains formed of several units (e.g. the 8-car formations of class 315s on TfL Rail), each unit has its own ac feed but there is only a low voltage control connection between them. But I'm now getting confused with how an S stock's electrical connections work. I understand that the compressors are on the DMs and can only take power from the shoegear on their respective DM. I understand that all cars on S stock are powered, but I don't think all cars have shoegear. How are the non-shoe fitted cars powered? A bit like 92TS. On S stock the DM cars and the MS cars have collector shoes and associated line protection. The M1 cars traction is fed from the adjacent DM car and the M2 car from the MS car. Train formations are DM- M1 - M2- MS - MS - M2 - M1 - DM for an S8 train. The S7 trains have only one M2 car, so one of the MS cars does not feed traction equipment on an adjacent car. |
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Post by norbitonflyer on Dec 30, 2019 10:58:56 GMT
A bit like 92TS. On S stock the DM cars and the MS cars have collector shoes and associated line protection. The M1 cars traction is fed from the adjacent DM car and the M2 car from the MS car. Train formations are DM- M1 - M2- MS - MS - M2 - M1 - DM for an S8 train. The S7 trains have only one M2 car, so one of the MS cars does not feed traction equipment on an adjacent car. So electrically an S8 can be considered as four units, albeit unlike 1992TS there are permanent mechanical couplings between the M1 and M2 cars in each half-train? |
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Post by Dstock7080 on Dec 30, 2019 11:04:16 GMT
So electrically an S8 can be considered as four units, albeit unlike 1992TS there are permanent mechanical couplings between the M1 and M2 cars in each half-train? For traction voltages yes. As I posted up-thread there is a 400v auxiliary bus-line along 4-cars (or 3- & 4- for S7) S Stock have permanent couplings between all cars. |
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Post by bomo on Dec 30, 2019 13:24:42 GMT
All DC emus built for the former Southern Region network from BR days onwards had/have all of the shoe gear within the unit interconnected. I recall reading of one incident where a section had been isolated to allow a train to be evacuated, but another train was mistakenly allowed to move forward to a point where it formed a bridge between the section it was taking power from and the isolated section. Fortunately a quick-thinking staff member supervising the evacuation recognised the significance of the sound of the stalled train's compressors starting up. Yes. That incident was on the approach to Waterloo. It was a mass baleout by passengers after the service ground to a halt. Total chaos as I recall. |
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Post by norbitonflyer on Dec 30, 2019 20:47:02 GMT
As I posted up-thread there is a 400v auxiliary bus-line along 4-cars (or 3- & 4- for S7). Does that mean that if a DM and the nearest MS are both gapped, there is no auxiliary power to that half of the train? (What does the S in MS stand for?) |
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Post by t697 on Dec 30, 2019 21:25:27 GMT
MS car in S stock jargon is Motor Shoegear, i.e. motor car with shoegear. |
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Post by goldenarrow on Dec 30, 2019 22:29:20 GMT
MS car in S stock jargon is Motor Shoegear, i.e. motor car with shoegear. Thanks, looking back, I think my list probably predates S stock by a good few years. |
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Post by philthetube on Jan 2, 2020 21:59:53 GMT
A few points worth making about this discussion.
All? rail gaps on the underground are long enough for trains not to be able to bridge them and transfer current to a dead section.
Before an evacuation staff should lay short circuiting devices, (SCD) at both ends of a train to prevent recharge of current.
Trains can be rear (or front) tripped by many things beside trainstops, footballs or dead badgers located between the positive rail and running rail being the most common ones.
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Post by MoreToJack on Jan 2, 2020 22:38:14 GMT
Sectionalisation gaps, that is gaps located at substations, should all be over a train’s length to avoid livening up a section ahead or in rear.
However there are other gaps, particularly around point work, which are not sectionalisation gaps and may only be a small distance apart. As these are all fed by the same substation(s), on the same traction current section, there is no danger of a train livening these up. It is this ‘kind’ of rail gap that caused the aforementioned ‘gapped’ train at Baker Street.
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Post by 100andthirty on Jan 3, 2020 7:59:50 GMT
MoreToJack.....what you say is only true on lines where the front shoe of the train is connected by a power bus line to the rear shoe of the train. There are no trains like this on LU. Section gaps need to be longer than the show spacing on a car. In practice 15m gaps are sufficient to make sure a train can't electrically bridge the gap. The only places where a trains length is provided is where the floating earth LU system connects to the NR third rail/track earth system.
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Post by Dstock7080 on Jan 3, 2020 8:32:17 GMT
The only places where a trains length is provided is where the floating earth LU system connects to the NR third rail/track earth system. Certainly not trains length gaps at either Putney or Chiswick, standard 15m gaps provided.  |
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Post by Dstock7080 on Jan 3, 2020 9:06:09 GMT
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North End
Beneath Newington Causeway
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Post by North End on Jan 3, 2020 13:31:48 GMT
A few points worth making about this discussion. All? rail gaps on the underground are long enough for trains not to be able to bridge them and transfer current to a dead section. Before an evacuation staff should lay short circuiting devices, (SCD) at both ends of a train to prevent recharge of current. Trains can be rear (or front) tripped by many things beside trainstops, footballs or dead badgers located between the positive rail and running rail being the most common ones. AFAICR there are still a few gaps which are less than 15 metres, although rare. So staff remain trained to work on the basis that a train may bridge any gap, even if this isn’t true in the vast majority of cases. It’s also often overlooked that a train is essentially passing over a gap from one section to a other every time it changes from one line to another, for example when reversing via a crossover. |
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North End
Beneath Newington Causeway
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Post by North End on Jan 3, 2020 13:36:52 GMT
Sectionalisation gaps, that is gaps located at substations, should all be over a train’s length to avoid livening up a section ahead or in rear. However there are other gaps, particularly around point work, which are not sectionalisation gaps and may only be a small distance apart. As these are all fed by the same substation(s), on the same traction current section, there is no danger of a train livening these up. It is this ‘kind’ of rail gap that caused the aforementioned ‘gapped’ train at Baker Street. A sectionalisation gap is a specific term, and such gaps are provided as part of the traction earth detection system, and refers to the gap separating two sectionalisation areas. A sectionalisation area involves multiple traction current sections, and is separated from its neighbour inside the substation as well as trackside. There’s no special term for a gap which is long enough not to be bridged by a train, normally 15 metres. |
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Post by MoreToJack on Jan 3, 2020 13:50:50 GMT
Oversimplification on my part, combined with posting whilst half asleep. 😅
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Post by zbang on Jan 3, 2020 17:03:55 GMT
That's exactly what I was referring to <mumble> posts ago. |
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